The key makes three threats and Black has three knight moves - each which neatly dictates which of the individual threats will work.
Notice there is a 1-1 correspondence between the number of Black's moves and the number of threats - this sometimes referred to as an ideal Fleck.
Here we have quite possible the economy record for a Fleck. 7 threats separated by the moves of Black and only 6 pieces. Some people have suggested adding a wP on a7 to make it an ideal Fleck. The key is obvious due to the unprovided check 1...Ra1+, but you cannot argue with the economy for such a task.
1.Rh8! (>2.B any)
Here is what appears to be the (non-battery) record for a Fleck. The flight taking key sets up eight threats which are nicely differentiated:
This problem is one of my favorites because of the open position and differentiation.
Here is beautiful Fleck with the record of 14 threats differentiated. The threats are all given by the B+R battery. A nice key that exposes the wK to three checks. I'll leave it to you find which threats force which battery mates. 1.Kxc4! (2.Re~)
Here is something fun. I love 7th rank magic and this has plenty of it. The give and take key sets up several threats with 5 threats forced.
Now we come to what is called a secondary Fleck. The key makes a single threat. If the bS on e5 is lifted off the board then there are 6 mates available. However, wherever the bS lands only one of the mates works. Beautiful differentiation.
The mate 1...Sxc6+ 2.Qxc6 is what is known as an elimination mate or total defense: it eliminates all of the threats.
Stocchi pulls off a primary and secondary Fleck.
So the three threats are separated. A random move of the bSg5 defeats all threats by pinning the wQ. Now, there are 3 mates 1...S5~ (2.Qxh5/Bxh5/Rxe4) which are forced by the landing spots of the bS.
At the age of 71 Mansfield had something to say about the Fleck theme. Here the traditionalist comes through with a modern problem. This time the Fleck is impure - there are Black moves that allow duals, otherwise known as a partial Fleck. The key makes eight threats that are forced by eight 'best' moves for Black.
Here is another partial Fleck. The key makes six threats, but this time there are six Black moves that separate the threats. However, all other Black moves intentionally allow all six threats, not duals, triples, quadruples, or quintuples. The judge of the tourney, Barry Barnes, coined the term essential Fleck. I'll leave it to you to figure out what these moves are.
Here is one of my experiments with the Fleck theme. By looking at the problem you can see that the Fleck will have to be partial. Here I offer a combination of Novotny and Fleck.
1...dxe3 e.p. 2.fxe3
I like the way the threats Rxd4 and f4 are forced and the elimination en passant defense.
Finally, here is the only pure Fleck problem that I have made. A king on its home square with the ability to castle has the ability to make four mates (including the castle). This ideal Fleck with these four mates. There is also a nice little try 1.Bf2? c3!
The problem is after Milan Velimirovic's problem www.yacpdb.org/#26857, which shows a Fleck with these four mates and uses similar mechanisms. My problem is more economic and demonstrates an ideal Fleck, whereas Velimirovic's has Black duals.